1. Field of the Invention
The present invention relates generally to automatic brake actuators for towed vehicles, and more particularly to an automatic hydraulic brake actuator which is integrated with the hitch assembly of a towed vehicle. Forward pressure on the hitch assembly by the towed vehicle (trailer or another vehicle in tow) compresses the assembly, causing a brake master cylinder to be actuated to supply braking pressure to the brakes of the towed vehicle. The device is easily installable and removable, by means of quick disconnect fittings and pins.
2. Description of the Prior Art
The towing of small and lightweight trailers and the like by larger vehicles, is generally done without regard to braking means on the towed vehicle. If the towed vehicle is sufficiently light, very little additional load is placed upon the brakes of the towing vehicle in such circumstances. However, as the size and weight of the towed vehicle increases in proportion to the towing vehicle, brakes for the towed vehicle, in some form or another, are almost universally required.
Accordingly, numerous different types of brakes and brake actuation systems have been developed for trailers and towed vehicles, using electric, hydraulic, pneumatic, and other actuating means for the towed vehicle. Smaller towing vehicles, as well as relatively smaller trailers and the like which are equipped with any braking means at all, are generally equipped with hydraulic brakes as opposed to other operating principles. The use of hydraulic brakes with such vehicles, and particularly in the case of an automobile or other powered vehicle which is being towed on its own wheels, generally precludes the use of any braking system other than hydraulic. Yet, trailer brake systems which are hydraulically connected into the braking system of the towing vehicle are cumbersome and complex, thus leading to the operator sometimes failing to connect the systems. Electric brakes on the towed vehicle provide some means around the above complexity, but require special brakes on the towed vehicle, as well as a reasonably powerful electric power source for the trailer brakes.
The present invention responds to the above problems by tapping into the hydraulic braking system of the towed vehicle, assuming it is so equipped, and relying upon the principle of the inertia of the towed vehicle against the tow hitch or tow bar to actuate the hydraulic brakes of the towed vehicle. Various devices have been developed in the past to actuate the hydraulic brakes of a trailer, but none operate in the manner of the present invention, as will be shown in the following discussion of the prior art of which the present inventor is aware.
U. S. Pat. No. 3,856,363 issued on Dec. 24, 1974 to John T. Kasselmann describes an Adjustable Linkage For Transmitting The Output From A Sensor To A Control Valve. The disclosure is directed to a trailer or towed vehicle braking system which is interconnected with and actuated from the brake system of the towing vehicle. The system is relatively complex, and incorporates vacuum boosted hydraulic brakes in the towed vehicle. Accordingly, both a hydraulic brake line and a vacuum boost line must be connected between the towing vehicle and the trailer brake system. The present system is completely portable and easily installable and removable between the towing and towed vehicles, and does not require any brake line connection between the towing and the towed vehicles, unlike the Kasselmann assembly.
U. S. Pat. No. 4,453,620 issued on Jun. 12, 1984 to William G. Angus et al. describes an Automatic Safety Brake Actuation Tongue For Towed Vehicles. The relatively complex assembly comprises three telescoping tubes with a slide bar within the innermost tube. The device is a permanent component of the trailer tongue, and is not removable from the trailer, whereas the present device is removably securable to the receiver hitch of the towing vehicle. Angus et al. utilize a complex mechanical pushrod linkage to actuate the emergency brakes of the trailer, and in addition generally disclose an internal hydraulic surge brake within the permanently mounted telescoping trailer tongue assembly. Details of the hydraulic brake means are not disclosed.
U. S. Pat. No. 5,013,059 issued on May 7, 1991 to Bernhardt P. Goettker describes an Actuator/Coupler comprising a telescoping trailer tongue arrangement having a specially configured hydraulic brake master cylinder therein. The present invention uses a conventional, "off the shelf" master cylinder, for economy and ease of maintenance. The Goettker assembly is permanently mounted to the trailer or towed vehicle, thus requiring a separate tow bar or tongue assembly for each towed vehicle or trailer. The present invention overcomes this redundancy by providing a single device which is quickly and easily attachable and detachable to the towing vehicle, in the manner of a conventional draw bar and receiver hitch configuration. Hydraulic components of the present invention are readily accessible on the exterior of the device, for simplicity and ease of maintenance. The present device also provides for the lockout of braking action during backing maneuvers, as does the Goettker device, but requires manual reactivation of the braking system when backing is completed. Goettker's device automatically reactivates the automatic braking system when a single backing maneuver is completed, but oftentimes a towed vehicle or trailer must be moved back and forth a few times for optimal positioning. Goettker's device provides no advantage here, as the operator must manually lock out the braking action each time the vehicles are moved forward, or tensile force is applied between towing and towed vehicle, in any backing operation.
U. S. Pat. No. 5,213,396 issued on May 25, 1993 to Larry L. Avery et al. describes a Towed Vehicle Brake Activation Method And Apparatus. The device comprises a hitch ball mounted to the end of a generally vertical bar, which is in turn pivotally secured within a hitch assembly removably attachable to the towing vehicle. The forward rocking or pivoting of the hitch bar due to braking of the towing vehicle, actuates a hydraulic master cylinder which provides hydraulic fluid under pressure to the brakes of the towed vehicle. The present system also attaches removably to the towed vehicle and uses self contained hydraulic braking means, but is considerably more compact with its two telescoping components. The present system has no components which extend significantly below the attached hitch ball or the hitch receiver of the towing vehicle. This is a critical distinction, as relative angular motion between the towing and towed vehicles over uneven terrain can often cause low mounted portions of the hitch assembly to drag on the surface.
U. S. Pat. No. 5,246,243 issued on Sep. 21, 1993 to Larrey Carr describes a Towing Vehicle Mounted Receiver Hitch Actuating A Towed Vehicle's Brake System. The Carr device is a receiver hitch assembly which is permanently mounted to the towing vehicle by an intermediate portion of the assembly in place of the conventional hitch bar receiver. The present device is removably installable to a conventional receiver permanently mounted to the towing vehicle. Carr also provides no adjustability for initial brake activation, brake pressure, or reverse lockout means, all of which are provided by the present device.
U. S. Pat. No. 5,342,117 issued on Aug. 30, 1994 to Thomas D. Price et al. describes a Brake Pulsing Apparatus adapted for use in a powered vehicle, rather than a towed vehicle or trailer. The system relies upon an inertial switch (pendulum) to actuate braking, and also utilizes a timer relay to actuate and deactivate the brakes rapidly for a pulsing, antilock braking system. The permanently installed apparatus and principles of operation of the Price et al. system are beyond the scope of the present invention. While Price et al. note that their system may incorporate an interconnected relay and/or solenoid to coordinate the pulsing of trailer brakes with the towing vehicle brakes, the system does not utilize inertial forces in the hitch assembly to actuate a brake master cylinder, as in the present invention.
Finally, U. S. Pat. No. 5,522,649 issued on Jun. 4, 1996 to Axel Stender et al. describes a Process And Apparatus For Monitoring A Trialer (sic) Brake For Overload. The apparatus is a complex electromechanical system, using a differential force sensing device to sense longitudinal forces applied between the towing vehicle (tractor) and trailer. This sensor provides a signal to the braking system to modulate the trailer brakes to produce the desired trailer braking force, with the force sensing unit between tractor and trailer continuing to provide feedback during the operation. The present device is completely independent of the brake system of the towing vehicle, and is portable.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.